Question

Write the formula for a complex formed between fe3 and ethylenediamine (nh2ch2ch2nh2), with a coordination number of 6.

Answer 1

We have to get the formula of the complex formed between Fe³⁺ and ethylenediamine.

The formula of the complex is: [Fe(en)₃]³⁺, where, en is abbreviation of ethylenediamine.

Ethylenediamine (en) is a bidentate ligand as it contains two donating sites (-NH₂ groups). Three ethylenediamine co-ordinate to central metal ion, Fe³⁺ and forms [Fe(en)₃]³⁺ with a co-ordination number of six.

Answer 2

Answer: The formula of the complex will be $[Fe(NH_2CH_2CH_2NH_2)_3]^{3+}\text{ or }[Fe(en)_3]^{3+}$

Explanation:

Coordination number in a complex is defined as the number of ligands that are attached to the central metal atom.

• If the ligand is unidentate, it will occupy 1 place around the central metal atom.
• If the ligand is bidentate, it will occupy 2 places around the central metal atom.
• If the ligand is tridentate, it will occupy 3 places around the central metal atom.

We are given:

A metal ion having formula $Fe^{3+}$ and ligand attached to it is ethylenediamine (shortly named as 'en')

Coordination number of the complex is 6

We know that, 'en' is a bidentate ligand and does not carry any charge on it

Hence, the formula of the complex will be $[Fe(NH_2CH_2CH_2NH_2)_3]^{3+}\text{ or }[Fe(en)_3]^{3+}$